Process for the production of washing- and cleaning-active granules

ABSTRACT

The invention concerns a method of converting aqueous surfactant mixtures, in particular aqueous pastes of surfactants with washing properties such as fatty-alcohol sulphates, in particular tallow alcohol sulphates and/or C 12  -C 18  fatty-alcohol sulphates, monosalts of sulphonic fatty-acid methyl esters and their di-salts, alkylglusoside compounds, etc., into concentrated granular material with a long shelf life by granulation. The aqueous surfactant mixture, which includes as a viscosity-control agent alkoxylates of mono- and/or polyhydric alcohols with 8-40 carbon atoms which have up to 20 ethylene oxide and/or propylene oxide groups, is granulated together with fine-particulate water-soluble and/or water-insoluble solids compatible with washing and/or cleaning agents to give a free-running compound. At least part of the water content of the granular material thus produced is preferably then removed by drying, in particular in a fluidized bed.

BACKGROUND OF THE INVENTION

This invention relates to a process for converting water-containingpreparations of washing- and cleaning-active surfactant compounds intostorable surfactant granules and into storable detergents in granularform.

Considerable and, at the same time, greatly increasing interest is beingshown in the use of oleochemical surfactant compounds in detergents andcleaning products. The primary considerations in this regard are basedon the one hand on the fact that surfactant compounds of this type canbe obtained from renewable vegetable and/or animal raw materials,although on the other hand it is above all the high ecologicalcompatibility of selected components of this type to which crucialsignificance is attributed. An example of one such class of oleochemicalsurfactant compounds are the known fatty alcohol sulfates which areprepared by sulfatization of fatty alcohols of vegetable and/or animalorigin containing predominantly 10 to 20 carbon atoms in the fattyalcohol molecule and subsequent neutralization to water-soluble salts,more particularly the corresponding alkali metal salts. Of particularpractical significance in this regard are the sodium salts of fattyalcohol sulfates which are based on at least predominantly linear fattyalcohols or corresponding fatty alcohol mixtures containingapproximately 12 to 18 carbon atoms in the fatty alcohol molecule.Tallow alcohol sulfates (TAS) containing predominantly saturated C₁₆₋₁₈residues in the fatty alcohol are already of considerable interest forthe production of laundry detergents, more particularly in solid form,although significant detergent properties may also be attributed tofatty alcohol sulfates (FAS) which cover a broader range in regard tothe length of their carbon chains. Thus, C₁₂₋₁₈ fatty alcohol sulfateshaving a high percentage content of the lower fatty alcohols of thisrange, for example based on coconut oil or palm kernel oil, representparticularly important anionic surfactants for use in detergents andcleaning products. There are numerous references to this effect in therelevant specialist literature, cf. H. Baumann "Neuere Entwicklungen aufdem Gebiet fettchemischer Tenside", Fat Sci. Technol., 92 (1990) 49/50and the literature cited therein. European patent application 342 917also describes detergents in which the anionic surfactants consistpredominantly of C₁₂₋₁₈ alkyl sulfates.

The economic synthesis of light-colored anionic surfactants based on FASis now established state of the art. The corresponding surfactant saltsaccumulate in the form of water-containing preparations in which thewater contents may vary from approximately 20 to 80% and, moreparticularly, from approximately 35 to 60%. Products of this type have apaste-like to cuttable consistency at room temperature, the flowabilityand pumpability of the pastes being limited or even completely lost foractive substance contents of only about 35% by weight, so that thesubsequent processing of the pastes, particularly their incorporation insolids mixtures, for example in solid detergents and cleaning products,involves considerable problems. It is possible to obtain free-flowingFAS powders by conventional drying processes, particularly in spraydrying towers. However, there are serious limitations in this regardwhich, in particular, jeopardize the economy of using FAS surfactants onan industrial scale. Tower-dried TAS powder, for example, shows a verylow apparent density, so that there are unprofitable aspects to thepackaging and marketing of this detergent raw material. However, even inthe production of spray-dried powder, safety considerations cannecessitate such restrictive operation of the spray drying tower thatpractical difficulties arise. Thus, safety-based investigations oftower-dried powder based on TAS or FAS having active substance contentsof 20% or higher show that the spray drying of formulations of this typeis only possible to a very limited extent and, for example, requirestower entry temperatures below 200° C.

Comparable difficulties or other difficulties are involved in theconversion of water-containing, more particularly paste-form,preparations of numerous other washing- and cleaning-active surfactantcompounds into storable dry products. Further examples of anionicoleo-chemical surfactant compounds include the known sulfofatty acidmethyl esters (fatty acid methyl ester sulfonates, MES) which areprepared by α-sulfonation of the methyl esters of fatty acids ofvegetable and/or animal origin containing predominantly 10 to 20 carbonatoms in the fatty acid molecule and subsequent neutralization towater-soluble monosalts, more particularly the corresponding alkalisalts. The corresponding α-sulfofatty acids or disalts thereof areformed therefrom by ester cleavage and show specific washing- andcleaning-active properties in the same way as mixtures of disalts andsulfofatty acid methyl ester monosalts. However, comparable problemsalso arise with other classes of surfactants where attempts are made toproduce the corresponding surfactant raw materials in solid or granularform, as for example with washing- and cleaning-active alkyl glycosidecompounds. To obtain light-colored reaction products, their synthesisgenerally requires a final bleaching step carried out, for example, withwater-containing hydrogen peroxide, so that in this case, too, moderntechnology leads to the water-containing paste form of the surfactant.Water-containing alkyl glycoside pastes (APG pastes) are moresusceptible, for example, to hydrolysis or microbial contamination thancorresponding solids. In their case, too, simple drying by conventionalmethods involves significant difficulties. Finally, however, even thedrying of a water-containing paste of the alkali metal salts ofwashing-active soaps and/or of alkyl benzenesulfonates (ABS pastes) canalso involve considerable problems.

It is also desirable, above all for economic reasons, to limit thequantity of water to be introduced into the process as far as possible.Accordingly, the smallest possible quantity of water is best used in thewater-containing surfactant pastes. However, the degree of concentrationis limited by the viscosity behavior of the water-containing pastes.Only raw materials which can still be processed, i.e. for example areflowable and pumpable, in the process can be introduced into theprocess. It is known that, particularly for detergents and cleaningproducts, for example for laundry detergents, important anionicsurfactants, such as the alkali metal salts of ABS, fatty alcoholsulfates, fatty acids, α-sulfonated fatty acids and correspondingα-sulfofatty acid esters, can only be worked up into flowable andpumpable pastes using relatively considerable quantities of water. Thus,ABS salt pastes and pastes of tallow alcohol sulfates having watercontents of 40 to 60% by weight are being processed in practice at thepresent time. In addition, the paste viscosity of water-containingmixtures of the type in question is still greatly dependent ontemperature so that pastes of the type in question cannot be usedwithout difficulties at room temperature and elevated temperatures, forexample in the range from 50° to 70° C., have to be applied.

Further investigations in the field in question have revealed dramaticdeteriorations in the processability of water-containing mixed pastes inone important special case: the paste viscosity allows ABS and TASpastes each having solids contents of 50 to 60% by weight to beseparately processed. However, if an attempt is made to mix theseseparately processable pastes to obtain a homogeneous anionic surfactantmixture for subsequent incorporation in detergent formulations, there isa dramatic increase in viscosity in the paste mixture for basically thesame solids content. This phenomenon is observed both when the ABS pasteis added to the FAS paste and vice versa. Even mixing ratios of 9:1 or8:2 lead to a solidified, water-containing material which can no longerbe processed.

The teaching of U.S. Pat. No. 4,495,092, the entire contents of whichare incorporated herein by reference, describes the use of C₈₋₄₀alcohols which are substituted by 1 to 5 hydroxyl groups and/or ontowhich up to 15 mol ethylene oxide and/or propylene oxide are added pertool alcohol as viscosity regulators for high-viscosity industrialsurfactant concentrates of the synthetic anionic surfactant type.Corresponding water-containing pastes of alkyl sulfates, alkylarylsulfates and α-sulfofatty acid esters having a surfactant content of atleast 30% by weight are mentioned in particular. According to thisteaching, the addition of the above-mentioned viscosity regulators inquantities of 1 to 15% by weight, based on the quantity of surfactant,leads to viscosities of the particular surfactant concentrate of at most10,000 mPa.s at 70° C. (Hoppler falling ball viscosimeter). Mixtures ofsaturated and unsaturated fatty alcohols containing up to 8 tool EOand/or PO units are particularly preferred viscosity regulators. Theviscosity behavior of water-containing pastes of mixed surfactants and,in particular, the dramatic increase in viscosity when water-containingABS and TAS pastes are mixed is not discussed in this publication.

The problem addressed by the present invention was to provide analternative method of processing water-containing, more particularlypaste-form, surfactant preparations into dry, more particularlyfree-flowing and concentrated surfactant granules. The invention isbased on the disclosure of U.S. Pat. No. 4,495,042, but extends theprinciples described therein beyond existing knowledge.

DESCRIPTION OF THE INVENTION

In a first embodiment, therefore, the present invention relates to aprocess for the production of washing- and cleaning-active granules bygranulation of a mixture of a water-containing surfactant preparationand one or more water-soluble and/or water-insoluble solids, so thatfree-flowing granules are formed. The concentrated surfactantpreparations contain alkoxylates of monohydric and/or polyhydric C₈₋₄₀alcohols containing up to 20 ethylene oxide and/or propylene oxidegroups as viscosity regulators. The free-flowing granules are at leastpartly freed from their water content by drying.

The process according to the invention is particularly suitable for thegranulation of surfactant pastes of which the surfactant components aresolids at temperatures of up to at least 40° C. and which per se have ahigh viscosity, their viscosity being reduced in accordance with theinvention by the use of the viscosity regulators. It is thus possible atthe same time to reduce the processing temperature and/or to reduce thesurfactant solids content in the water-containing paste material. Thenew process is particularly suitable for the use of anionic surfactantpastes based on alkyl sulfates, alkyl sulfonates, alkylaryl sulfonates,α-sulfofatty acid esters, α-sulfofatty acid disalts and/or soaps. Moreparticularly, it has surprisingly been found that mixed pastes of thetype in question, which for example contain mixtures of surfactantcompounds based on ABS and TAS in any quantities, can be converted intocomparatively free-flowing and pumpable pastes by addition of relativelylimited quantities of fatty alcohol alkoxylates. According to theinvention, suitable viscosity regulators are, in particular, alkoxylatesof fatty alcohols of synthetic and/or natural origin of the typetypically used as so-called nonionic surfactant components in moderndetergents and cleaning products, particularly laundry detergents, wherethey are generally used in the form of a mixture with anionicsurfactants of the type described above. However, the process accordingto the invention is also suitable for the use of water-containing pastesof washing-active alkyl glycoside compounds.

The invention thus provides for the economic production of virtually anymixtures of, for example, anionic surfactants and selected nonionicsurfactants in dry form which can be controlled and optimized in regardto their composition, i.e. in regard to type and/or quantity, by theparticular application envisaged. On the other hand, the interactionbetween the nonionic surfactants and the water-containing anionicsurfactant pastes it is specifically used to control and reduce theviscosity of the raw materials. According to the invention, it ispossible in this regard to use these advantages on the one hand toobtain compounds of high surfactant content in the form of dry,free-flowing granules and, on the other hand, to make the technologyaccording to the invention of mixing, granulation and subsequent dryingavailable for the production of detergents and cleaning products,particularly laundry detergents, as a whole or at least in the form ofsuch a premix containing the main components that subsequent furthermixing with selected, for example particularly temperature-sensitive,components is all that is necessary to obtain the final laundrydetergent.

Accordingly, in another embodiment based on the granulation processdescribed above, the invention relates to a process for the productionof highly concentrated surfactant granules which may be used assurfactant-rich compounds for the production of detergents and cleaningproducts.

In another embodiment, the invention relates to a process for theproduction of storable and free-flowing detergents and cleaningpreparations, more particularly laundry detergents, which are alsosuitable for subsequent mixing with, in particular,temperature-sensitive constituents of the detergents and cleaningproducts.

The compounds preferably used as viscosity regulators in accordance withthe present invention are derived from monohydric alcohols of natural orsynthetic origin having carbon chain lengths in the above-mentionedrange. Aliphatic alcohols of this type are known to be derived fromnatural fats and oils and are obtained, for example, by reduction of thecorresponding fatty acid esters. These so-called fatty alcohols arelinear and may be saturated or unsaturated. Viscosity regulators basedon alkoxylated fatty alcohol mixtures of the type used as nonionicsurfactant components in the production of detergents and cleaningpreparations are particularly suitable for the purposes of theinvention. Accordingly, suitable viscosity regulators are, inparticular, ethoxylates of linear and/or branched monofunctional fattyalcohols containing approximately 10 to 20 carbon atoms, particularsignificance being attributed to the range of 12 to 18 carbon atoms inthe alcohol components of the fatty alcohol or fatty alcohol mixture. Inone preferred embodiment, these fatty alcohols are alkoxylated with, onaverage, approximately 2 to 10 EO groups, particular significance againbeing attributed to the range from about 3 to 8 EO groups. Acommercially available nonionic surfactant component of this type is,for example, the product marketed by applicants under the name "DehydolLST 80:20" which is a mixture of 80 parts by weight C₁₂₋₁₈ fattyalcohols containing on average 5 EO units and 20 parts by weight of aC_(12/14) fatty alcohol containing 3 EO units. This nonionic surfactant,which is used in numerous laundry detergents, is an extremely usefulviscosity regulator for the purposes of the invention. However, alcoholcomponents having a branched carbon chain may also be used as aliphaticalcohols or adducts suitable as viscosity regulators. Examples ofalcohols having a branched carbon chain are oxo alcohols and Guerbetalcohols, i.e. alcohols branched in the 2-position obtained by oxosynthesis or by the so-called Guerbet reaction. Polyfunctional alcoholsand alkoxylates thereof which are also suitable for the purposes of theinvention are mentioned in U.S. Pat. No. 4,495,092 where such compoundsas 12-hydroxystearyl alcohol, 9,10-dihydroxystearyl alcohol and ethyleneoxide products thereof are named by way of example as the basic alcoholcomponent.

It has been found that an effective improvement in the flowability ofwater-containing anionic surfactant pastes can be obtained even withonly small additions of the nonionic surfactant according to theteaching of U.S. Pat. No. 4,495,092, not only is this the case withselected individual anionic surfactants or water-containing pastesthereof, instead even a few percent of the nonionic surfactant added toa completely solidified ABS/TAS paste guarantees the requiredflowability and pumpability. In a preferred embodiment of the invention,therefore, the viscosity regulators are used in quantities of at leastabout 2% by weight and preferably in quantities of at least about 5% byweight, based on the solid weight of the generally anionic surfactantcomponent of the mixture in the water-containing preparation. Quantitiesof the nonionic viscosity regulators of up to about 15% by weight can beparticularly useful, so that particular significance is attributed tothe range of about 5 to 15% by weight.

The invention described in detail in the following reference by way ofexample to the conversion of water-containing FAS pastes intofree-flowing granules. The measures and process parameters described indetail hereinafter may also be broadly applied on the basis of generalchemical knowledge to other water-containing, more particularlypaste-form, surfactant preparations of the type in question here.

The water-containing FAS mixtures used in the flowable and pumpablesurfactant preparations are reaction products from the sulfatization andsubsequent water-containing/alkaline neutralization of the particularfatty alcohol used. The mixtures in question are generally mixtures ofcorresponding FAS types having different chain lengths with a preferablylinear fatty alcohol radical within the C₁₂₋₁₈ range mentioned. Thewater content of these FAS mixtures is preferably in the range fromabout 20 to 80% by weight and, more preferably, in the range from about30 to 50% by weight. The preferred working temperature (temperature ofthe surfactant paste) is either room temperature or a moderatelyelevated temperature, for example in the range from 40° to 60° C. Thegranulation process is carried out as follows:

In a suitable mixing and granulating machine, for example in an Eirichmixer, a Lodige mixer (for example a Lodige ploughshare mixer) or aSchugi mixer, the water-containing FAS nonionic surfactant mixture onthe one hand and water-soluble and/or water-insoluble solids on theother hand are introduced and mixed with one another at peripheralspeeds of the mixing elements of preferably 2 to 7 m/s (ploughsharemixer) or 5 to 50 m/s (Eirich, Schugi) and, more preferably, 15 to 40m/s in such quantities and with such intensity that free-flowinggranules are formed. The grain size of the granules may be determined inadvance in known manner. The mixing process requires only a very shorttime, for example of about 0.5 to 10 minutes and, more particularly,about 0.5 to 5 minutes (Eirich mixer, Lodige mixer), to homogenize themixture and to form the free-flowing granules. By contrast, where aSchugl mixer is used, a residence time of 0.5 to 10 seconds is normallysufficient to obtain free-flowing granules. The ratios in which thecomponents are mixed and, more particularly, the quantities of solidadded have to be adapted to the quantity of water introduced through theFAS mixture in such a way that the homogenized mixture ofwater-containing surfactant preparation and added solid is able to formthe free-flowing granules. The quantity of solid required is normallylarger, the higher the water content of the surfactant mixture. However,the free-flowing granules initially formed are not required to showprolonged stability in storage. According to the invention, the granulesare preferably transferred to the drying stage while they are stillmoist, i.e. immediately after granulation. In the preferred embodimentof the invention, drying is carried out in a fluidized bed. Basically,however, there is no need for any subsequent drying step to produce thefree-flowing granules. However, drying is advantageous and thereforepreferred because surfactant granules of increased surfactant contentare obtained in this way. It may be necessary, particularly wheresurfactant mixtures of low concentration, for example containing morethan 50% by weight and, in particular, more than 60% by weight water,are used to dry the granules initially formed to obtain the preferredminimum content of 20% by weight surfactant in the granules. Drying maybe carried out to the particular final content of unbound or even boundwater in the granules.

In another preferred embodiment, undried granules are mixed in any ratiowith partly or completely dried granules. "Completely dried" isunderstood to be the state in which the unbound water and any boundwater remaining have been removed from the granules.

Fluidized-bed drying is a preferred method of drying because it providesfor rapid drying of the outer surface of the granules with intensivemovement and mixing of the granules, thus counteracting undesirableagglomeration of the still moist granules.

In one particular embodiment, it is possible in the described mixing andgranulation stage to produce granules with such a degree of tackinessthat, basically, the granules might be expected to stick to one anotherso firmly that they could not be separated in the immediately followingdrying stage. According to the invention, the still moist granulesaccumulating are powdered with a dust-fine or powder-formauxiliary--best immediately after their production--and the granulesthus intermediately stabilized are introduced into the drying stagewhere the state of free-flow of the granules is then rapidly achieved,even under comparatively mild drying conditions.

Drying and, in particular, fluidized-bed drying is preferably carriedout at temperatures of the gas phase below 200° C. and, more preferably,at temperatures in the range from about 70° to 160° C., for example attemperatures in the range from about 90° to 150° C. These temperaturesapply primarily to the gas phase. In one preferred embodiment, the finaltemperature of the granules is comparatively low and, for example, doesnot exceed 80° to 90° C. and, preferably, is no higher than 75° C.

The solids used in the granulation stage for partly drying thewater-containing surfactant preparation may be corresponding ingredientsfrom typical formulations of detergents and/or cleaning products,although they may also be foreign substances providing they arecompatible with the application envisaged for the surfactants. It willbe generally be preferred to use ingredients of detergents and/orcleaning preparations. One particular advantage of the process accordingto the invention is that there is very considerable freedom in regard tothe choice of these solid mixture components. The reason for this liesin the fact that the granulation process according to the invention withthe preferably following drying stage is carried out under suchcomparatively mild conditions that only in exceptional cases is thereany danger of unwanted secondary reactions in the granulation and/ordrying step. General specialist knowledge may be applied in this regard.Thus, particularly temperature-sensitive mixture constituents, forexample of laundry detergents, of the type used for example as bleachesof the perborate type, will have relatively little significance.Preference will be attributed instead to water-soluble and/orwater-insoluble solids which can be safely mixed with thewater-containing surfactant preparations, granulated and subsequentlydried under the described working conditions. Accordingly, typicalexamples of suitable water-soluble solids are inorganic salts, forexample soda, alkali metal silicates, more particularly waterglasspowder, sodium sulfate and/or phosphate salts, such as sodiumpyrophosphate and sodium tripolyphosphate.

However, in addition to or instead of the use of water-soluble solids inthe granulation stage, the teaching according to the invention alsoencompasses the use of corresponding insoluble, preferably fine-particlematerials. The particle size of the preferred solids is less than 1 mmand, more particularly, less than 100 μm, for example no more than 30μm. Typical examples from the field of detergents and/or cleaningproducts are additives of the type used as so-called builders forbinding alkaline earth metal ions and hence for eliminating waterhardness. Examples are fine-particle crystalline zeolites, moreparticularly sodium zeolite NaA in detergent quality, of which at least80% preferably consists of particles smaller than 10 μm in size (volumedistribution: Coulter Counter). Other examples of preferred solids arehydrotalcites, water-insoluble and crystalline layer silicates,abrasives, such as mineral powders and the like.

One particular aspect of the invention is the use of preferably driedand finely redivided granules from the production line as a solidmixture constituent for working up further quantities of thewater-containing surfactant preparations. This embodiment of theinvention is characterized in particular by complete or partialrecycling of the granules produced by the process according to theinvention, more particularly the dried granules. Details of thisparticular embodiment are given in the following.

For the particular mixing ratios between the surfactants on the one handand the solids on the other hand to be used in the mixing andgranulation stage, it may be useful to adapt these mixture constituentsto the corresponding demand for the components in the detergents and/orcleaning products to be ultimately produced. More particularly, theratio of anionic surfactants to the fine-particle solids used, forexample, in laundry detergents may serve as guides for the compositionof the mixture to be granulated. The need to use various solid detergentconstituents--again best in adapted ratios to one another--may bederived from such considerations. One such case generally arises whenthe water content of the water-containing surfactant mixturenecessitates the use of such large quantities of dry solids that thequantity of this solid in the granules formed would bedisproportionately large for the particular application. This isexplained in the following with reference to an example:

The waterglass content of laundry detergents is comparatively small,based on the formulation as a whole, amounting for example to between 2and 5% by weight. By contrast, it may be desirable to mix in very muchlarger quantities of anionic surfactant based on fatty alcohol sulfate,for example quantities of 20 to 30% by weight, based on the finaldetergent as a whole. If an FAS surfactant mixture of relatively highwater content were to be used to carry out the process according to theinvention, considerably larger quantities of waterglass than would bedesirable in the final detergent would have to be mixed in to establishthe state of a free-flowing powder in the mixing and granulation stageif waterglass powder were to be used as the sole solid. Accordingly, itis advisable in this case to use other dry detergent constituents, forexample soda and/or sodium sulfate.

If, on the other hand, the solids used are of the type present or atleast potentially present in large quantities in typical detergentformulations, the desired percentage composition of the granulesaccording to the invention may be linked to the proportional mixturedetermined in advance by the overall detergent formulation. Typicalexamples of this are mixtures of the water-containing surfactant pastescontaining sodium zeolite, soda and/or sodium sulfate.

One particularly important embodiment of the invention is characterizedby the above-mentioned partial or complete recycling of the granules,preferably the dried granules, to the mixing and granulation stage. Inone preferred embodiment, which is particularly suitable for continuousoperation, the entire solid phase added in the mixing and granulationstage is formed from recycled material which consists of already driedgranules and which, therefore, already contains considerable quantitiesof anionic surfactant, i.e. preferably more than 25% by weight, based onthe dried granules used as the solid. The dried granules used as solidin the mixing and granulation stage are first size-reduced, for exampleunder the effect of the mixing tools or in a standard mill. The granulesmay be recycled once or even several times, for example 2 to 8 times.The advantages of recycling are quite clear. In the process according tothe invention, surfactant is concentrated in the granules to a fixed,predetermined level. By virtue of the comparatively low melting pointsof important detergent-quality surfactants, for example FAS compoundsand, more particularly, corresponding FAS mixtures, the enrichment ofthe granules to approximately 100% surfactant (sum of anionic surfactantand nonionic surfactant) will be of relatively little significance inpractice. In this embodiment of the process, however, considerablyhigher surfactant contents can be adjusted in the granules than in theembodiment where the water-containing mixture is passed only oncethrough the mixing and granulation zone. In the embodiment where thegranules are recycled, FAS contents of at least 30% by weight and,preferably, at least 35% by weight can readily be established in thegranules. It is possible in accordance with the invention to increasethe corresponding surfactant content to at least 45% by weight or evento at least 50% by weight. A surfactant content of 30 to 75% by weight,based on the dry granules, is particularly desirable. The higher thesurfactant content of the granules, the stronger the tendency of themixture to soften under the conditions of fluidized-bed drying. Theabove-mentioned powdering with solid dry mixture components, for examplewith dried zeolite NaA of detergent quality, can be particularly usefulin this regard.

The particle size range of the granules formed and the average particlesize are adjusted in known manner by adaptation of the workingconditions in the granulation stage. According to the invention,granules having particle sizes in the range from about 0.01 to 3 mm(sieve analysis) and, more particularly, in the range from about 0.05 to2 mm can be produced without difficulty. In one important embodiment ofthe invention, the dried granules are graded by removal of unwanted fineand oversize particles in known manner. In another important embodimentof the invention, the fractions thus removed may be returned to themixing and granulation stage and used as the solid, even when it is notintended to recycle the granulated and dried granules.

The physical properties of the granules may also be largelypredetermined in other ways. Thus, the hardness of the granules and, inparticular, their abrasion resistance can be modified, for exampleincreased, for example by using suitable auxiliaries, for example smallquantities of polymer compounds of the type typically used in detergentsand cleaning products. Examples of such polymer compounds are thepolyacrylates and polyacrylate copolymers known as builders which may beused, for example, with relative molecular weights in the range from30,000 to 100,000. Auxiliaries of this type may be added to the mixturein the actual mixing and granulation stage, although they may also besubsequently applied to the preformed granules before or during thedrying stage.

However, the process according to the invention may also be modified ina totally different form and used for the easier production of granulesof the described type. According to the invention, it is possible forexample not only to introduce water-containing surfactants in the mixingand granulation stage, other desired components of the final detergentand/or cleaning product may be introduced at least partly aswater-containing material into this stage of the process. Thismodification is illustrated by the following example: zeolite NaA isknown to accumulate during its production as an water-containingsuspension (master batch) which may contain more than 50% by weightwater and which is usually spray-dried to a powder-form solid. Accordingto the invention, the zeolite may be introduced into the mixing andgranulation stage at least partly in the form of this suspension or evenin the form of an incompletely dried product so that it may then bedried in admixture with the surfactant and the dry solids added to formgranules. An embodiment such as this can be of particular advantagewhere it is intended to recycle the dried granules and, in this way, tointroduce the component required as solid into the mixing andgranulation stage through the desired end product.

Zeolite materials of the last-mentioned type and also other typicalauxiliaries of detergents and cleaning products are in turn capable ofpartly binding water. Examples of auxiliaries of this type are anhydroussoda and anhydrous sodium sulfate which are capable of bindingconsiderable quantities of water in the form of water ofcrystallization. One embodiment of the invention uses this ability tointernally bind water for additional drying (internal drying) of thegranules formed in the process according to the invention. However, ithas been found in this regard that, where for example water-containingFAS pastes and dehydrated soda or dehydrated sodium sulfate are mixedand granulated in such quantitative ratios that almost all the water ofthe FAS paste introduced is bound by the crystal binding of this waterto soda or sodium sulfate, the granulation process can still be carriedout, but the products formed are not entirely satisfactory.Corresponding granules of, for example, soda and FAS paste which aresolid and free-flowing at room temperature agglomerate in storage,particularly if they are exposed to slightly elevated temperatures inthe meantime. Thus, where solids which bind water of crystallization areused, as in one preferred embodiment of the invention, the water contentis reduced to such an extent in the drying step that the bound waterpresent as water of crystallization is at least partly removed.Accordingly, the water contents of the preferred dried granulesaccording to the invention are comparatively low. The unbound watercontent is preferably below 8% by weight and more particularly below 5%by weight, based on the dried granules. Water bound in crystal form orwater bound into the molecular structure can be present in limitedquantities in the mixture although the stability of the granules instorage will be higher, the lower the extent to which in particular thewater of crystallization content of the end product is also reduced.This embodiment will naturally be of little significance in cases wherethe surfactant granules are to be rapidly further processed. If thegranules are to be marketed as raw materials, greater significance willbe attributed to this particular embodiment.

If the preferred small quantities of the nonionic surfactant componentof 2 to 15% by weight, based on the solids of the generally anionicsurfactant in the surfactant paste, are used to regulate viscosity inthe production of the free-flowing granules, mixing ratios of anionic tononionic surfactant that are comparatively low in nonionic surfactantscompared with typical formulations of detergents and cleaning productswill be present in the final granules. Although this may be of nosignificance to the teaching according to the invention of improvedproduction of the surfactant granules in question, it must be taken intoaccount when the granules are mixed to form the final detergent orcleaning product. The use of these comparatively small quantities ofnonionic surfactant may even be a preferred embodiment of the processaccording to the invention. This is generally the case when theprocessing conditions selected for the granulation and the preferablysubsequent drying of the granules on the one hand and the volatility ofthe nonionic surfactants used as viscosity regulators on the other handare likely to prompt objections on the grounds of so-called plumingwhich occurs in the towers used for the spray-drying of active-substancemixtures containing nonionic surfactant. However, it is important inthis regard to bear in mind the fact that the processing conditions and,in particular, the drying temperatures for the granulation processaccording to the invention are comparatively mild in the context of theteaching of the earlier application cited at the beginning, so thatobjections of the type just mentioned are minimized from the outset inthis case.

In addition, the invention opens up new possibilities for carrying outthe granulation process and, more particularly, the following dryingstage. The effective reduction of viscosity in accordance with theinvention provides for such low processing temperatures for thegranulation stage (for example in the range from 20° to 40° C.) thatobjections based on the potentional volatility of the nonionicsurfactant mixture component would have no foundation. The preferablyfollowing drying step may also be carried out at the same lowtemperatures or at least at comparably low temperatures. This is madepossible by the application of reduced pressure in the drying stage, theparticular working pressures to be applied being adaptable in knownmanner to the particular process parameters selected.

The above-described possibilities for carrying out the process accordingto the invention represent another important embodiment of theinvention. In this embodiment, the mixing ratio of anionic to nonionicsurfactants ultimately required in practice is actually established inthe preliminary granulation stage of the process. In other words, thetotal nonionic surfactant content required as viscosity regulator in thefinal laundry detergent is introduced into the granules together withthe anionic surfactants.

For the reasons explained above, however, it may still be appropriate tolimit the nonionic surfactant content, for example to quantities of atmost about 80% by weight and, more particularly, less than 50% byweight, based on the total quantity of nonionic surfactant in thelaundry detergent. Nevertheless, a quantity of nonionic surfactantexceeding the range of U.S. Pat. No. 4,495,092, and, hence, about 15% byweight (based on anionic surfactant) will still be used as viscosityregulator in the last of the above-described embodiments of theinvention. As mentioned above, the particular quantity of nonionicsurfactant to be selected will also be determined by the particularobjective in question, i.e. whether to produce anionic surfactantgranules of high surfactant content or whether to use the processaccording to the invention the production of detergents as a whole.

The teaching according to the invention enables the granulation processto be carried out with pastes having a very limited water content, evenat very low temperatures, i.e. for example in the range from about 20°to 40° C. Accordingly, even temperature-sensitive materials, such assodium perborate or enzymes or enzyme-containing preparations may now beused as solid granulation aids. By virtue of the fact that granulationcan be carried out at such low temperatures, certaintemperature-dependent modifications of solid mixture components whichbind water of crystallization can be used to facilitate the process. Forexample, it is known that, at temperatures of up to about 32° C., sodaforms the decahydrate which then changes with release of water into theheptahydrate which is stable up to about 35° C. and, finally, changesinto the monohydrate under the effect of a further increase intemperature. The same applies to sodium sulfate. Bearing in mind thatone of the objects of the granulation process is to achieve theintermediate water-binding solidification of the mixture introduced intothe granulation stage, the advantage afforded by the invention ofworking at very low granulation temperatures immediately becomes clear.Comparatively small quantities of the solid mixture component (in thiscase soda or sodium sulfate) are required to bind the quantities ofwater introduced through the water-containing surfactant pastes andhence to facilitate granulation. The increase in temperature in thegranules only takes place in a subsequent preferred stage of theprocess, namely during fluidized-bed drying, where the intermediatelybound water of crystallization can be released from the granules withoutany damage.

However, the invention also affords the following advantage: by virtueof the relatively low surfactant viscosity, relatively fine droplets areproduced when the surfactant pastes are sprayed into the mixing andgranulation unit. This provides for more uniform distribution of thefree-flowing phase. Where high-speed mixers, for example of the Eirichor Schugi type, are used, a fluidized product zone into which thesurfactant paste is sprayed is built up in the mixing zone. Theintensive shear forces lead to very fine distribution of the relativelyfree-flowing water-containing surfactant.

The granules according to the invention can have an increased apparentdensity, more particularly in relation to corresponding spray-driedmaterials. Typical granules according to the invention normally have anapparent density of at least about 350 g/l and preferably of at leastabout 500 g/l. Apparent densities of 600 to 800 g/l are particularlypreferred.

As mentioned at the beginning, the process according to the inventionmay be carried out with a broad range of water-containing surfactantmixtures, including in particular mixtures of surfactants which aresufficiently dimensionally stable and solid at room temperature andwhich are present as water-based pastes containing the surfactantsdispersed in the aqueous phase, above all during their production and/orworking up. One important example of surfactants such as these are theα-sulfofatty acid methyl ester monosalts and/or the so-called disalts.In their production on an industrial scale, the monosalts of thesulfofatty acid methyl esters (MES) actually accumulate in the form of amixture with limited quantities of disalts which, as already known, areprepared by partial ester cleavage with formation of the correspondingα-sulfofatty acids or their disalts. The disalt content of theseMES-based surfactants is typically below 50 mol. % of the anionicsurfactant mixture, for example in the range up to about 30 mol. %. Theteaching according to the invention is suitable for application toMES-based surfactant mixtures of the type in question and tocorresponding mixtures having relatively high disalt contents up to thepure disalts.

A preferred water-containing MES starting material are the reactionproducts of relatively high water content from the sulfonation andsubsequent water-containing/alkaline neutralization of the particularfatty acid methyl ester. The reaction products in question are generallymixtures of corresponding MES types having different chain lengths withpreferably linear C₁₂₋₁₈ fatty acid residues. The water content of thesecrude MES products may be from about 20 to 80% by weight and, moreparticularly, from about 30 to 60% by weight.

Surfactant compounds based on alkyl glycosides and their production,particularly in the form of water-containing bleached pastes, aredescribed in detail, for example, in International patent application WO90/03977. Surface-active reaction products of this type are anotherexample of the application of the process according to the invention forthe production of dry surfactant-based granules. The process accordingto the invention may be generally used for working up water-containingpreparations of surfactant compounds at least substantially solid atroom temperature from the class of anionic, nonionic, zwitterionicand/or cationic surfactants, the choice of corresponding surfactantcompounds of high ecological compatibility being preferred.

EXAMPLES Example 1

1.5 kg of a surfactant mixture of 95% by weight Texin ES 68 (a productof Henkel KGaA containing 53% by weight of the sodium monosalt ofα-sulfotallow fatty acid methyl ester and 11% by weight of the disodiumsalt of sulfotallow fatty acid and also 29% by weight water) and 5% byweight of a C₁₂₋₁₈ fatty alcohol containing 5 ethylene oxide (EO) groups(Dehydol LT5, a product of Henkel KGaA) were granulated with 1.5 kg sodafor 3 minutes in a 10 liter Eirich mixer at a peripheral speed of 24 m/scorresponding to a rotational speed of 2,500 r.p.m. (star whirler). Thegranules were then dried in a fluidized bed (Aeromatik) for 60 minutesat an air entry temperature of 70° C. Free-flowing granules containing1.5% by weight water for an apparent density of 750 g/l were obtained.The content of washing-active substance (WAS, titratable--Eptonmethod--anionic surfactant content, in the present case: sulfotal-lowfatty acid methyl ester and disalt content; accuracy±2% by weight) was34% by weight, the disalt content amounting to 5.5% by weight.

Example 2

1.5 kg of the surfactant mixture mentioned in Example 1 were granulatedwith 750 g soda for about 1 minute at 25° C. in an Eirich mixer (10liters, star whirler, 2,500 r.p.m., 24 m/s). The granules were thendried in a fluidized bed (Aeromatik) for 60 minutes at an air entrytemperature of 50° C. Free-flowing granules containing approximately 7%by weight water for an apparent density of 590 g/l were obtained. TheWAS content of the granules was 49% by weight.

Example 3

150 kg of the surfactant mixture mentioned in Example 1 were granuledwith 150 kg soda for 2 minutes in a 300 liter Eirich mixer (starwhirler, 700 r.p.m., 18 m/s). The granules were then dried in afluidized bed (Heinen) for 20 minutes at an air entry temperature of100° C. Free-flowing granules containing approximately 1% by weightwater for an apparent density of 780 g/l were obtained.

Example 4

150 kg/h of a surfactant mixture of 92% by weight Sulfopon T 55 (aproduct of Henkel KGaA containing approx. 54% by weight tallow alcoholsulfate and approx. 41% by weight water) and 8% by weight Dehydol LT5were continuously granulated with 180 kg/h soda in a Schugi mixer (26m/s). The-granules obtained were dried for 10 minutes at 110° C. The WAScontent was 28% by weight and the water content 4% by weight for anapparent density of 350 g/l.

Example 5

1.5 kg of a surfactant mixture of 95% by weight Texin ES 68 and 5% byweight of a fatty alcohol containing 7 EO (Dehydol LT7, a product ofHenkel KGaA) were mixed with 750 g sodium sulfate and dried as inExample 1. After drying, the granules contained 0.7% by weight water and53% by weight WAS, including 8% by weight disalt. The apparent densitywas 650 g/l.

Example 6

1.5 kg of the surfactant mixture mentioned in Example 4 were granulatedwith 1.5 kg dried sodium zeolite A as in Example 1 and dried for 60minutes at an air entry temperature of 90° C. The product had a watercontent below 1% by weight and an apparent density of 600 to 700 g/l(depending on the fine-particle and oversize-particle components).

Example 7

1.5 kg of the surfactant mixture mentioned in Example 4 were mixed with1.5 kg soda, granulated and dried as described in Example 6. Another 450g of the surfactant mixture were then applied to the granules formed inan Eirich mixer. The granules with their increased WAS content wereagain dried in a fluidized bed. This process could be repeated 7 timeswithout the individual granules sticking to one another either in themixer or in the fluidized bed. The granules had a WAS content of 65% byweight and a water content of less than 1% by weight for an apparentdensity of 640 g/l.

Example 8

1.5 kg of the surfactant mixture mentioned in Example 4 were granulatedwith 1.5 kg sodium perborate monohydrate as described in Example 1. Thegranules were dried in a fluidized bed for 60 minutes at an air entrytemperature of 70° C. The granules had a water content of less than 5%by weight for an apparent density of 680 g/l.

Example 9

2.5 kg of the surfactant mixture mentioned in Example 4 were granulatedwith 1.5 kg of a porous and absorbent detergent additive [containing 71%by weight zeolite NaA and 4% by weight of a copolymeric polyacrylate(Sokalan CP5, a product of BASF), based on anhydrous substance, and 20%by weight water] and dried as described in Example 6. Another 500 g ofthe surfactant mixture were then applied and the new granules richer insurfactant were again dried. The granules had a WAS content of 49% byweight and a water content of less than 1% by weight for an apparentdensity of 630 g/l.

Example 10

389 g of a surfactant mixture consisting of 98% by weight of anwater-containing tallow alcohol sulfate paste (55% by weight solidscontent) and 2% by weight of the product "Dehydol LT 7" were applied to786 g of a "surfactant-free" powder-form detergent having thecomposition shown below and granulated in the same way as described inExample 6. The product was dried in a fluidized bed for 60 minutes at anair entry temperature of 90° C. The product had an apparent density of760 g/l, a water content of 4.6% by weight and a WAS content of 21.3% byweight.

    ______________________________________                                        Composition of the "surfactant-free" detergent (in % by                       ______________________________________                                        weight):                                                                      C.sub.12-18 sodium fatty acid soap                                                                    2.3                                                   Sodium silicate (Na.sub.2 O:SiO.sub.2 1:3.3)                                                          4.7                                                   Sokalan CP5 ® (a product of BASF;                                                                 6.3                                                   copolymer of acrylic acid)                                                    Zeolite (based on anhydrous substance)                                                                32.7                                                  Sodium carbonate, calcined                                                                            18.9                                                  Sodium sulfate          28.1                                                  Water and other constituents                                                                          7.0                                                   ______________________________________                                    

What is claimed is:
 1. A process for the production of surfactantgranules which comprises mixing a water-containing surfactant paste withone or more water soluble or water insoluble solids to directly formgranules comprised of at least about 20% by weight of surfactant,wherein said water-containing surfactant paste is comprised of ananionic surfactant or an alkyl glycoside or a combination thereof and aviscosity regulator selected from the group consisting of an ethoxylatedor propoxylated C₁₀₋₂₀ monohydric alcohol having a degree ofalkoxylation of up to 20, an ethoxylated or propoxylated C₈₋₄₀polyhydric alcohol having a degree of alkoxylation of up to 20, andmixtures thereof.
 2. The process of claim 1 further comprising the stepof drying said granules in a fluidized bed.
 3. The process of claim 1wherein the temperature of the gas phase used in said fluidized bed isless than about 200° C.
 4. The process of claim 1 wherein said anionicsurfactant is selected from the group consisting of an alkyl sulfate,alkyl sulfonate, α-sulfofatty acid ester, α-sulfofatty acid disalt, anda soap.
 5. The process of claim 12 wherein said viscosity regulator is aC₁₀₋₂₀ monohydric alcohol having a degree of ethoxylation of from about2 to about
 10. 6. The process of claim 5 wherein said degree ofethoxylation is from about 3 to about
 8. 7. The process of claim 1wherein the concentration of said viscosity regulator is at least 2% byweight of said anionic surfactant or said alkyl glycoside or saidcombination thereof.
 8. The process of claim 7 wherein the concentrationof said viscosity regulator is at least 5% by weight of said anionicsurfactant or said alkyl glycoside or said combination thereof.
 9. Theprocess of claim 8 wherein the concentration of said viscosity regulatoris from about 5% to about 15% by weight of said anionic surfactant orsaid alkyl glycoside or said combination thereof.
 10. The process ofclaim 1 wherein said water-soluble solid is soda, an alkali metalsilicate, or sodium sulfate.
 11. The process of claim 1 wherein saidwater-insoluble solid is zeolite NaA, hydrotalcite, mineral powder, orcrystalline layer silicate.
 12. The process of claim 1 wherein saidgranules have a surfactant content of at least 25% by weight of drygranules.
 13. The process of claim 12 wherein said granules have asurfactant content of from about 30% to about 75% by weight of drygranules.
 14. The process of claim 1 wherein said granules are comprisedof an anionic surfactant which is a solid at a temperature of at leastroom temperature.
 15. The process of claim 14 wherein said granules arecomprised of an anionic surfactant which is a solid at a temperature ofabout 40° C.